[DFS] Remove opened file check

Remove opened file check in dfs_file_open function. It will be replaced with POSIX flock/fcntl.

components/dfs/src/dfs_file.c

@@ -8,6 +8,7 @@
  * 2005-02-22     Bernard      The first version.
  * 2011-12-08     Bernard      Merges rename patch from iamcacy.
  * 2015-05-27     Bernard      Fix the fd clear issue.
+ * 2019-01-24     Bernard      Remove file repeatedly open check.
  */
 
 #include <dfs.h>
@@ -48,14 +49,6 @@ int dfs_file_open(struct dfs_fd *fd, const char *path, int flags)
 
     LOG_D("open file:%s", fullpath);
 
-    /* Check whether file is already open */
-    if (fd_is_open(fullpath) == 0)
-    {
-        rt_free(fullpath); /* release path */
-
-        return -EBUSY;
-    }
-
     /* find filesystem */
     fs = dfs_filesystem_lookup(fullpath);
     if (fs == NULL)